Bad service

I bought a laptop from Phone choice in 2015 November and I app**** for a debt review ,when time went on I realized that they were not paying my debts as agreed ,then Finchoice handed me over to Hammondpole Attorneys and I made arrangements to pay up the account.In July 2020 I paid them up and they provided me with a paid up letter which I still have as proof.After a few months I got a call from Nimble Group saying that I owe Finchoice and don't remember taking anything from them.It really hurts me because I can't do anything I even took the matter to my lawyers but they can't help me.